U.S. patent number 5,511,268 [Application Number 08/286,965] was granted by the patent office on 1996-04-30 for construction of large structures by robotic crane placement of modular bridge sections.
This patent grant is currently assigned to The United States of America as represented by the Secretary of Commerce. Invention is credited to James S. Albus, Ken Goodwin, Yair Tene.
United States Patent |
5,511,268 |
Albus , et al. |
April 30, 1996 |
Construction of large structures by robotic crane placement of
modular bridge sections
Abstract
A system for rapid, cost-effective construction of highway
bridges, traffic verpasses and bypasses, and causeways over water
or wetlands utilizes light-lift crane structures together with
modular, light-lift bridge sections and an enhanced stabilized
crane, using controlled cables, to improve the safety and
efficiency of the construction process. Stabilization of the
payload against pendulation and rotation enables safe operation in
harsh environmental situations such as wind. The construction
system utilizes continuous site assembly processes for building
bridges and causeways from repetitive modular elements. In some
embodiments, the system uses the payload (one or more modular
bridge sections) as a component of a stable lifting and positioning
system, thereby eliminating the need for heavy auxiliary lifting
equipment such as spreader bars and platforms. Lifting cables of
the crane are directly attached to the bridge payload, which
becomes part of the lifting system during placement. Other
embodiments utilize installed modular elements as a staging
platform for constructing subsequent modular elements.
Inventors: |
Albus; James S. (Kensington,
MD), Goodwin; Ken (Alexandria, VA), Tene; Yair (N.
Potomac, MD) |
Assignee: |
The United States of America as
represented by the Secretary of Commerce (Washington,
DC)
|
Family
ID: |
23100899 |
Appl.
No.: |
08/286,965 |
Filed: |
August 8, 1994 |
Current U.S.
Class: |
14/77.1; 212/312;
212/324 |
Current CPC
Class: |
E01D
21/06 (20130101) |
Current International
Class: |
E01D
21/06 (20060101); E01D 21/00 (20060101); E01D
015/12 () |
Field of
Search: |
;212/205,214,215,216,217,218,219 ;14/77.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0102900 |
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Sep 1982 |
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EP |
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0076597 |
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Apr 1983 |
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EP |
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0164936 |
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Dec 1985 |
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EP |
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1558417 |
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Jan 1969 |
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FR |
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1249307 |
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Sep 1967 |
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DE |
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1-310003 |
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Dec 1989 |
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JP |
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908989 |
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Apr 1980 |
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SU |
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1096328A |
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Apr 1982 |
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SU |
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Primary Examiner: Neuder; William P.
Attorney, Agent or Firm: Oliff & Berridge
Claims
What is claimed is:
1. A crane capable of lifting and carrying modular bridge sections
for overpass bridge construction, the crane comprising:
a first supporting leg frame including a first pair of supporting
legs, each of said legs comprising structure providing mobility of
said crane and having a first length;
a second supporting leg frame including a second pair of supporting
legs, each of said legs comprising structure providing mobility of
said crane and having a second length, longer than said first
length; and
a plurality of trusses connected between said first and second
pairs of supporting leg frames, said trusses supporting heavy-lift
corner cables capable of lifting and carrying said modular bridge
sections;
wherein said first supporting leg frame is movable on an installed
bridge section fixed to an existing section and wherein said second
supporting leg frame is movable on said existing section.
2. A crane according to claim 1, further comprising at least one
light-lift platform movably supported by said trusses, said at
least one light-lift platform capable of assembling said modular
bridge sections.
3. A crane according to claim 1, comprising four heavy-lift corner
cables, each of said cables disposed at a corner section of said
crane, each said cables being driven by a winch.
4. A crane according to claim 1, comprising at least six heavy-lift
corner cables supporting said modular bridge sections in six
degrees of freedom.
5. A crane according to claim 1, comprising two light-lift
platforms, said light-lift platforms stabilizing said modular
bridge sections during transport of said modular bridge
sections.
6. A crane according to claim 1, wherein said structure providing
mobility comprises wheels.
7. A crane according to claim 1, wherein a length of at least one
of said first and second supporting leg frames is adjustable.
8. A crane according to claim 1, wherein said second pair of
supporting legs are approximately twice as long as said first pair
of supporting legs.
9. A crane according to claim 1, wherein said first and second
pairs of supporting legs, said frame and said at least one
light-lift platform have a combined load rating less than a load
rating capacity of said bridge construction.
10. A lifting system comprising a plurality of cables and carrying
a payload, said cables arranged to support said payload in six
degrees of freedom, wherein said payload is used as a lifting
platform.
11. A method of constructing a bridge structure using a crane, the
crane comprising structure capable of lifting and carrying modular
bridge sections, the method comprising the steps of:
(a) assembling an initial bridge section having a predetermined
length;
(b) installing said initial bridge section;
(c) placing said crane on said initial bridge section;
(d) assembling with said crane a subsequent bridge section using
one of said initial bridge section and a previous subsequent bridge
section as a staging platform;
(e) lifting said subsequent bridge section with said crane and
stabilizing said subsequent bridge section;
(f) moving and carrying said subsequent bridge section to a next
position;
(g) attaching said subsequent bridge section to said bridge
structure; and
(h) repeating steps (d) through (g) until said bridge structure is
completely constructed.
12. A method according to claim 11, wherein said crane comprises at
least one light-lift platform, said lifting and stabilizing step
comprising stabilizing said subsequent bridge section in six
degrees of freedom.
13. A method according to claim 11, wherein said crane comprises a
plurality of heavy-lift corner cables, said lifting step comprising
securing said heavy-lift corner cables to said subsequent bridge
section and lifting said subsequent bridge section with said
cables.
14. A method according to claim 13, wherein said moving and
carrying step comprises rolling said crane on a wheel assembly to
said next position.
15. A method according to claim 11, wherein said moving and
carrying step and said attaching step comprise positioning and
attaching spudwells and pilings to an end of said subsequent bridge
section.
16. A method according to claim 15, further comprising driving said
pilings until said subsequent bridge section is fully
supported.
17. A method according to claim 11, wherein said assembling step
comprises assembling two skeleton sections on top of said initial
bridge section, said placing step comprising placing said crane on
sides of said skeleton sections such that said crane supports each
of said skeleton sections on opposite sides thereof, each of said
skeleton sections comprising legs with spud cans displaceable
between a transport position and an extension position, and wherein
prior to said attaching step, the method comprising lowering said
legs from said transport position to said extension position.
18. A method according to claim 11, wherein said crane is a
cantilever crane.
19. A method according to claim 11, wherein said crane is a
counterweight crane.
20. A method of constructing a bridge structure using a crane, the
crane comprising structure capable of lifting and carrying modular
bridge sections, the method comprising the steps of:
(a) assembling an initial bridge section having a predetermined
length;
(b) installing said initial bridge section;
(c) assembling two skeleton bridge sections on said initial bridge
section, said two skeleton bridge sections each having supporting
legs with spud cans displaceable between a transport position and
an extension position;
(d) placing said crane on said two skeleton bridge sections and
attaching said skeleton bridge sections to front and rear portions
of said crane, respectively;
(e) moving said crane and said skeleton bridge sections such that
said skeleton section attached to said first portion of said crane
approaches a next position;
(f) attaching said skeleton section attached to said front portion
of said crane to said bridge structure in said next position;
(g) lowering said legs of said skeleton section attached to said
front portion of said crane from said transport position to said
extension position and lowering said spud cans;
(h) releasing said skeleton section attached to said rear portion
of said crane;
(i) positioning a subsequent skeleton section behind said skeleton
section previously attached to said rear portion of said crane;
(j) moving said crane such that said skeleton section previously
attached to said rear portion of said crane is adjacent said front
portion of said crane and said subsequent skeleton section is
adjacent said rear portion of said crane;
(k) attaching said front and rear portions of said crane to said
skeleton sections, respectively; and
(1) repeating steps (e) through (k) until said bridge structure is
completely constructed.
Description
BACKGROUND OF THE INVENTION
The present invention is related to systems and methods of
constructing highway bridges, traffic overpasses, causeways and the
like, and more particularly, to a bridge constructing system using
light weight lifting equipment and modular light weight structural
elements, wherein the system integrates the lifting equipment with
the structure being erected using the structure as a crane
platform.
Construction of highway bridges and causeways requires special high
capacity lifting equipment, typically cranes. In most cases,
lifting is performed by cables or hydraulic jacks, providing three
or one degrees of freedom movement, respectively. Precise load
positioning and orientation of the load (roll, pitch and yaw) is
achieved by pulling with auxiliary tie lines or pushing with poles,
jacks or other external devices.
Lifting, carrying and final positioning of a payload that is not
fully constrained results in pendulation and rotation of the
payload, which reduces safety, requires more time to damp motion,
and in harsh environmental situations, such as high winds, may
cause shutdown and postponement of the lifting operation.
Feasibility, cost and construction time for erecting highway
bridges and causeway structures is typically governed by the
assembly method, capacity of available lifting equipment, weight
and number of the structural elements, organization of a
staging-storage area and transporting the structural elements and
lifting equipment from the production site to the erection
site.
Use of large preassembled structural elements can substantially
reduce construction time and cost. However, handling of the large
structural elements typically requires heavy lifting equipment,
such as cranes having spreader bars. If the assembly cranes are
heavier than the load that the bridge or causeway is intended to
carry, the assembled structure may have to be overdesigned to
support the assembly equipment.
The following publications are related to construction of bridge
structures.
U.S. Pat. No. 3,845,515 to Gelhard et al. discloses a system for
self-advancing construction of a conduit line. A railway is mounted
on each side of the conduit. An assembly scaffolding capable of
motion is suspended from the rails and is provided with a
progressing erection component cantilevered to overhang the most
forward assembled conduit section. The scaffolding accepts
construction components and progressively erects the components
along an intended route. The assembly scaffold is comprised of
several connected, mutually supported and series-arrayed assembly
sections. The front section of the assembly structure is developed
into a cantilevered erecting section, while the most rearward
assembly section is developed into a cantilevered material
receiving section. Sections in between the front and rear
cantilever sections are provided with controlled suspensions. An
assembly scaffold consisting of several sections is thus suspended
from its middle sections on travel rails of the previously erected
pipe railroad section, and may be supplied with construction
material from the rear. The materials are then transported to the
front progressing sections of the structure where they are used by
the cantilevered construction equipment to construct a further
forward section of the pipe railroad. When construction of that
section is completed, the entire assembly scaffold may move forward
by the corresponding new segment, and a new section may be
begun.
U.S. Pat. No. 3,385,455 to Dal Pont discloses an apparatus for
lifting, horizontally transporting and installing heavy loads, such
as metal lattice trusses, between spaced apart vertical support
points. The apparatus comprises spaced apart first and second
vertical support means against which rests each end of a
horizontally extending boom and respective tackle means supported
from spaced apart points along the boom. The boom and support means
constitute a rigid stationary structural assembly while a load is
being moved between the vertical support points. The assembly is
transferable as a unit to other locations.
U.S. Pat. No. 4,282,978 to Zambon discloses a bridge crane
comprising a framework consisting of a pair of parallel trusses
interconnected by end portals and long enough to extend across
three piers. Each truss has a bottom stringer formed on its
underside with tracks engaged above each pier by rollers mounted on
a pair of rocker arms, which are part of an undercarriage movable
on transverse guide rails. Top stringers of the trusses support a
trolley carrying hoists for raising and lowering transported
castings. Longitudinal movement of the framework relative to the
piers is brought about by a motor-driven capstan carried on the
framework.
U.S. Pat. No. 3,902,212 to Muller discloses a device for use in
building the superstructure of a multispan civil engineering work,
such as a bridge or elevated road. The superstructure comprises at
least one two-arm beam extending in a longitudinal direction
substantially symmetrically on both sides of a previously erected
pier. The device is comprised of a raised elongated scaffold E
having a median support adapted to rest on the pier. The scaffold
includes booms 1, 2 and 3. The booms 1 and 2 constitute rolling
tracks for carriages 4 and 5.
European Publication 0 102 900 A2 discloses a beam positioning
system having two parallel horizontal frames spanning over three
columns. Each frame has a top rolling track for mobile bogies that
move astride the frames and carry beam lifters. Each frame has a
parallel bottom rolling track for rollers at the top of each
column.
Japanese Publication 1-310003 (A) discloses a bridge building
method using a traveling frame lockable on an existing beam, a
lifter type crane, and a means to hang/support a beam block from
the lifter type crane.
Soviet Publication SU 908989 discloses a gantry type bridge
erection crane including a load carriage supporting beam 2, hinged
and fixed legs 8 and 10 and an operating mechanism. After bridge
supports and beams 12 and 13 are erected, crane columns 7, in the
next span are jacked up and mounted on the erected bridge beams.
The crane beam is then transferred to a new erection position, the
crane columns lowered, and freed temporary supports 4 moved
forward.
Soviet Publication SU 1096328 A discloses a bridge span assembly
method using mobile support gantries of adjustable height.
U.S. Pat. No. 3,027,633 to Murphy discloses a method and apparatus
for bridge construction in which a light-weight, temporary erection
span 11 is erected on a barge 12, hoisted into position between two
bridge piers, and used as a working platform for erecting a bridge
span. The method includes a deck traveler 17 equipped with two
stiff-leg derricks 17a and 17b mounted on a completed bridge span
18 and moving on skid beams mounted on the upper floor beams of the
completed bridge span.
U.S. Pat. No. 3,571,835 to Buechler discloses an apparatus for
concreting multiple section elevated structures. The apparatus
comprises two girders that are movable relative to one another. One
of the girders is a scaffold girder, and the other is an advancing
girder that supports the scaffold girder as it is advanced.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved
construction system and method that overcomes the above-described
problems.
It is another object of the invention to provide an improved system
for rapid, safe construction of highway bridges, overpasses,
bypasses and causeways.
These and other objects of the invention are achieved by providing
a crane capable of lifting and carrying modular bridge sections for
overpass bridge construction, including a first supporting leg
frame including a first pair of supporting legs, each of the legs
including structure providing mobility of the crane and having a
first length, a second supporting leg frame including a second pair
of supporting legs, each of the legs including structure providing
mobility of the crane and having a second length, longer than the
first length, and a beam or truss connected between the first and
second pairs of supporting leg frames, the beam or truss supporting
heavy-lift corner cables capable of lifting and carrying the
modular bridge sections. The first supporting leg frame is movable
on an installed bridge section fixed to an existing section, and
the second supporting leg frame is movable on the existing
section.
The crane may also include at least one light-lift platform movably
supported by the frame and capable of assembling the modular bridge
sections. Four to six heavy-lift corner cables, each driven by a
winch may be provided, wherein each of the cables is disposed at a
corner section of the crane. At least one of the first and second
supporting leg frames may be adjustable.
In accordance with another aspect of the invention, there is
provided a lifting system including a frame and a plurality of
cables for lifting and carrying a payload, wherein the cables are
arranged to support the payload in six degrees of freedom, and the
payload is used as a lifting platform.
In accordance with yet another aspect of the invention, there is
provided a method of constructing a bridge structure using a
cantilever crane, the cantilever crane including structure capable
of lifting and carrying modular bridge sections, and the method
including the steps of:
(a) assembling an initial bridge section having a predetermined
length;
(b) installing the initial bridge section;
(c) placing the crane on the initial bridge section;
(d) assembling with the crane a subsequent bridge section using one
of the initial bridge section and a previous subsequent bridge
section as a staging platform;
(e) lifting the subsequent bridge section with the crane and
stabilizing the subsequent bridge section;
(f) moving and carrying the subsequent bridge section to a next
position;
(g) attaching the subsequent bridge section to the bridge
structure; and
(h) repeating steps (d) through (g) until the bridge structure is
completely constructed.
The crane may include at least one or more light-lift platform,
wherein the lifting and stabilizing step includes stabilizing the
subsequent bridge section in six degrees of freedom. The crane may
further include a plurality of heavy-lift corner cables, wherein
the lifting step comprises securing the heavy-lift corner cables to
the subsequent bridge section and lifting the subsequent bridge
section with the cables.
The moving and carrying step and the attaching step may comprise
positioning and attaching spudwells and pilings to an end of the
subsequent bridge section.
In addition, the assembling step may include assembling two
skeleton sections on top of the initial bridge section, wherein the
placing step comprises placing the crane on the sides of the
skeleton sections such that the crane supports each of the skeleton
sections on opposite sides thereof, each of the skeleton sections
including legs with spud cans displaceable between a transport
position and an extension position, and wherein prior to the
attaching step, the method including lowering the legs from the
transport position to the extension position.
In accordance with yet another aspect of the invention, there is
provided a method of constructing a bridge structure using a crane,
the crane including structure capable of lifting and carrying
modular bridge sections, the method including the steps of:
(a) assembling an initial bridge section having a predetermined
length;
(b) installing the initial bridge section;
(c) assembling two skeleton bridge sections on the initial bridge
section, the two skeleton bridge sections each having supporting
legs with spud cans displaceable between a transport position and
an extension position;
(d) placing the crane on the two skeleton bridge sections and
attaching the skeleton bridge sections to front and rear portions
of the crane, respectively;
(e) moving the crane and the skeleton bridge sections such that the
skeleton section attached to the first portion of the crane
approaches a next position;
(f) attaching the skeleton section attached to the front portion of
the crane to the bridge structure in the next position;
(g) lowering the legs of the skeleton section attached to the front
portion of the crane from the transport position to the extension
position and lowering the spud cans;
(h) releasing the skeleton section attached to the rear portion of
the crane;
(i) positioning a subsequent skeleton section behind the skeleton
section previously attached to the rear portion of the crane;
(j) moving the crane such that the skeleton section previously
attached to the rear portion of the crane is adjacent the front
portion of the crane and the subsequent skeleton section is
adjacent the rear portion of the crane;
(k) attaching the front and rear portions of the crane to the
skeleton sections, respectively; and
(l) repeating steps (e) through (k) until the bridge structure is
completely constructed.
In accordance with still another aspect of the invention, there is
provided a counterweight lifting system for lifting and carrying a
first payload and a second payload, wherein the counterweight
lifting system is movably attachable to the first and second
payloads on opposite sides of a centerpoint, and a weight of one of
the first and second payloads is used to lift a weight of the other
of the first and second payloads.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other aspects and advantages of the present invention
will become apparent from the following detailed description of
preferred embodiments when taken in conjunction with the
accompanying drawings, in which:
FIG. 1 illustrates a crane in position on a bridge and a first
assembled section of an overpass in accordance with a first
embodiment of the invention;
FIG. 2 shows the light-lift platforms assembling overpass
components;
FIG. 3 shows the completed skeleton section of the overpass
bridge;
FIG. 4 illustrates the completed skeleton bridge section prior to
its attachment to the bridge structure;
FIG. 5 is a closeup view of the winch and heavy lift cables in the
first embodiment;
FIG. 6 illustrates a cantilever crane installed on top of a first
completed bridge section in accordance with a second embodiment of
the invention;
FIG. 7 illustrates the cantilever crane assembling a bridge
component skeleton section;
FIG. 8 shows the cantilever crane moving the completed bridge
section forward for attachment to the bridge structure;
FIG. 9 shows the skeleton section attached to the bridge
structure;
FIG. 10 illustrates the cantilever crane in a next position for
.assembly of the next section;
FIG. 11 illustrates a counterweight crane carrying a skeleton
section positioned on top of a skeleton causeway section in
accordance with a third embodiment of the invention;
FIG. 12 shows the counterweight crane advancing the skeleton
section to a next position;
FIG. 13 shows the skeleton section attached to the bridge
structure; and
FIG. 14 shows the causeway counterweight crane separated from the
attached skeleton section and ready to move backward and receive a
new skeleton section.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to FIG. 1, the construction system of a first embodiment
utilizes four preferably 42 foot sections of preassembled overpass
10 that are installed on an initial section of an existing bridge
12 using a conventional crane. The overpass crane 14 is
preassembled and installed on the 168 foot section of overpass and
the existing bridge as illustrated in FIG. 1.
The overpass crane 14 includes a first frame of supporting legs 16
each comprising wheels 18 adapted to roll on rails 20. A second
frame of supporting legs 22 similarly includes wheels 24 for
rolling on rails 26. Although wheels 18 and 24 are illustrated in
the figures, any suitable structure providing mobility of the crane
can be used, and the invention is not meant to be limited thereto.
Supporting legs 22 are about two times the length of supporting
legs 16 so that the crane 14 maintains an almost level attitude
while simultaneously engaging the existing bridge 12 and the
overpass sections 10. In one embodiment the legs are adjustable via
a telescoping arrangement (shown in phantom in FIG. 1).
A longitudinal truss structure 28 is connected between the first
and second frames of supporting legs. Referring to FIG. 5, the
overpass crane 14 includes heavy lift corner cables 30 disposed at
the corners of the crane 14 and driven by a winch 32 disposed on
the frame of supporting legs. The longitudinal truss 28 movably
supports two light lift platforms 34 that are capable of supporting
a load in six degrees of freedom. Such a platform is known in, for
example, U.S. Pat. No. 4,666,362 to Landsberger et al. and U.S.
Pat. No. 4,883,184 to Albus, the disclosures of which are hereby
incorporated by reference.
The light-lift platforms 34 are used for constructing modular
bridge sections in a known manner using an installed overpass
section as a staging platform (see FIG. 2). In addition, the
light-lift platforms stabilize the assembled skeleton overpass
section 36 during transport (see FIG. 3).
Referring to FIGS. 2 and 3, the light-lift platforms assemble
columns 101, transverse beams 102, longitudinal trusses 103, and
longitudinal ties 104 to complete a skeleton overpass section 36.
The heavy-lift corner cables are secured to the completed skeleton
preferably using a conventional twist-lock structure such that the
completed skeleton overpass section 36 acts as a lifting platform,
replacing the heavy spreader bar of the conventional crane. Using
the heavy-lift corner cables 30 and winch 32 to lift the skeleton
section 36 and the light lift platforms 34 to stabilize the
skeleton section 36, the crane 14 is rolled forwardly, carrying the
completed skeleton section for attachment in a next position, as
illustrated in FIG. 4. The light-lift platforms 34 add deck
sections to complete the overpass section. The crane 14 is then
ready to construct another skeleton overpass section using the just
installed overpass section as a staging platform. The truss
structure of the overpass sections is generally known and will not
be described in detail. Examples include U.S. Pat. No. 4,907,390 to
Tene and U.S. Pat. No. 4,827,688 to Tene, the disclosures of which
are hereby incorporated by reference.
Because the overpass crane 14 including supporting leg frames 16,22
rides on rails outside and/or above traffic lanes, the construction
system allows overpasses or bypasses to be constructed without
interrupting traffic flow all or most of the time.
In one alternative arrangement, the crane is constructed without
light lift platforms 34 and includes six to eight corner cables.
The corner cables are distributed from each corner to a midpoint of
a respective side of the skeleton section 36, providing support for
the skeleton section 36 in six degrees of freedom.
Referring to FIG. 6, a construction system of a second embodiment
is illustrated in accordance with a cantilever crane 40. In the
initial bridge construction, four preferably 42 foot sections of
bridge are constructed on land accessible to a conventional crane.
The preassembled sections are installed using a conventional crane.
A cantilever crane 40 is assembled on top of the completed bridge
section as illustrated in FIG. 6. The cantilever crane 40 includes
a light lift platform 34 to assemble columns, transverse beams,
longitudinal trusses and longitudinal ties as discussed above to
complete the skeleton of a preferably 168 foot bridge section as it
is pushed forward by a truck or pulled by cables and winches
(illustrated in FIG. 7). The light-lift platform 34 also positions
and attaches spudwells 42 and pilings 44 to the end of the skeleton
section (illustrated in FIG. 9). The cables supporting light-lift
platform 34 are reeved around pulleys fixed to corners of the
cantilever crane. The heavy-lift cables of the causeway crane are
attached to the skeleton using the twist-lock connector described
above, and the completed skeleton causeway section is moved forward
to a next position as illustrated in FIG. 8. Thus, the completed
skeleton acts as a lifting platform, replacing the heavy spreader
bar of the conventional crane.
The piles are lowered and driven in a known manner until the
causeway section is fully supported. Piles are preferable attached
every fourth bridge section. Finally, the causeway section is
completed by installing the remainder of the trusses and deck
plates. As shown in FIG. 10, the cantilever causeway crane 40 is
then moved forward to the end of the completed section.
The frame components are preferably formed of axially loaded
structural elements to substantially reduce the weight of the
structure supporting the payload, pulleys and winches, its own
weight, windloads and dynamic effects caused by moving the payload
and the like during the assembly process. As a result, the maximum
load supported by the substructure and foundations during the
construction process is preferably no greater than their load
bearing capacity during operation. The crane structure is designed
with axially loaded structural elements carrying the main vertical
loads. By having the main lifting cables attached to the four
corners of the crane structures, the load is transferred directly
to the legs, and axial loads are introduced to the top members of
the frames of supporting legs and top members of the longitudinal
trusses 28. The light lift platforms, used to assemble much lighter
components, are likewise made of cables and axially loaded
elements. Axially loaded elements, cables and trusses utilize the
maximum allowable stresses over their whole section and are
therefore lighter and more effective than bending elements (beams)
where the maximum allowable stresses are utilized only at extreme
edges or corners. This design criteria leads to lighter structure
of the overpass bridge, which in turn enables reduction in weight
of the lifting equipment and reduction of the additional loads
imposed on the existing bridge.
These weight savings can be applied to achieve cost savings,
reduced construction time and increase the span of bridges and
causeways.
Referring to FIG. 11, a construction system of a third embodiment
is illustrated in accordance with a counterweight bridge crane 50.
In this construction, two or more complete, preferably 168 foot
bridge or causeway sections are assembled by conventional cranes
where there is access such as on land, on a quay, or from a ship or
barge. After installation of the preassembled sections, two
skeleton sections, preferably each 168 feet long, are assembled on
top of the completed bridge or causeway. As shown in FIG. 11, the
counterweight crane 50 is assembled on top of the skeleton section.
The counterweight crane rear frame 48 is attached to the rear
section 52 of the skeleton section while the front frame 60 of the
counterweight crane is attached to the front section 54.
Wheels 68' fixed to counterweight crane 50 are disposed above and
below a rail fixed to the skeleton sections. Wheels 68' are
selectively lockable on the rail to prevent movement.
The rear frame 48, supported by rear cables 62 attached to the top
of center frame 56 utilizes the weight of skeleton section 52 and
additional bridge components like decks and nestable trusses as
counterweight for lifting and lowering into place the front
skeleton section 54. The front skeleton section 54 is suspended
from the crane front frame 60 and the center cables 66. The front
frame is supported to the top of center frame 56 by front cables
64. Skeleton section 52 rides on the assembled bridge using wheels
68 or the like. A service car with crane 70 can move on the front
frame 60 to assist in connecting the center cables 66 to the front
skeleton section 54 and in lowering the front legs 58.
The two skeleton sections 52 and 54 together with the counterweight
crane 50 are rolled forward on wheels 68, to the new position (FIG.
12) where section 54 is above its final position in the bridge. A
new, preferably 168 foot skeleton section 74 is then attached to
the rear of skeleton section 52.
Referring to FIG. 12, as the crane 50 together with the first
skeleton section 52 and the second section 54 are rolled forward,
spud cans and legs 58 are lowered from a transport position (FIG.
11) to an extension position (FIGS. 12 and 13). The counterweight
crane 50 lifts the second section 54 of the skeleton, pushes it
forward using compression rods 72, and lowers it into final
position as shown in FIG. 13 using the rear section 52 as
additional counterweight. The forward ends of the compression rods
72 are disconnected, and the front legs are adjusted to fully
support skeleton section 54.
The front frame 60 and service car 70 are lifted back using the
front cables 64 and center cables 66 using a compression rods 72
(FIG. 14). Additional legs and spud cans 76 are attached to the new
skeleton section 74, and the counterweight crane 50 is disconnected
from skeleton section 52 and rolled backward. The crane 50 is
attached to skeleton section 74 and the cycle repeats itself with
section 52 becoming the "new" section 54 and section 74 becoming
the "new" section 52. The crane 50 together with the two bridge
skeleton sections 52 and 74 ("new" 52, 54) are rolled forward to
the same position described in FIG. 11.
While the invention has been described in detail with reference to
preferred embodiments thereof, which are intended to be
illustrative but not limiting, various modifications of the present
invention may be made without departing from the spirit and scope
of the invention, which is defined by the following claims.
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